Finding the Fourth Proportional to 1,243.89, 1,715.90 and 911.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,243.89 : 1,715.90 = 911.57 : x
2. Step 2: Convert to fraction form
   1,243.89/1,715.90 = 911.57/x
3. Step 3: Cross multiply
   1,243.89x = 1,715.90 × 911.57
4. Step 4: Simplify right side
   1,243.89x = 1,564,149.83
5. Step 5: Solve for x
   x = 1,564,149.83/1,243.89
6. Step 6: Final answer
   x = 1,257.47